This invention relates to a fire-resistant elastic closure for openings in the form of a preformed composite block.
In structural components (walls, ceilings) classified under fire prevention regulations, openings are not permitted because, in the event of a fire, flames and smoke can spread through the openings into the adjoining rooms. Above all in cases where lines (cables, pipes) are passed through these openings, the material which is to be used to close the rest of the opening has to satisfy particular requirements. Hitherto, the following means have been used to seal openings of the type in question:
mineral fiber boards or loose mineral fibers in combination with fireproof coatings and putties,
mortar products,
fireproof pads and
polyurethane foam elements.
Some of these products have very good properties. However, the ideal solution lies in a combination of simple production and processing coupled with low material costs, high fire resistance and the possibility of rapid installation and removal.
A fireproof and smoke-proof closure for wall openings is known from German Utility Model G 87 16 908.6. This closure is made in the form of a conical stopper by foaming a fine-cell two-component foam in a suitable mold. In practice, it has been found that these conical stoppers are attended by handling difficulties which are aggravated by their tacky outer skin. In addition, numerous hollow molds have to be kept on hand in order to obtain stoppers differing in size.
A fire-retardant composite foam of polyurethane foam flakes is described in DE 35 42 326 C1. It is made by mixing the foam flakes with intumescent compounds which expand in the event of fire as a binder and/or additive and then press-molding the resulting mixture. Intumescent compounds in the form of expanded graphite may be used as the additive while intumescent compounds in the form of an epoxy resin with a melamine hydrohalide as binder may be used as the binder. The composite foam thus obtained is suitable as a composite foam panel which is placed over surfaces to be protected.
The present invention relates to a fire-resistant elastic closure for openings in the form of a preformed composite block of
a) at least one type of elastically compressible particles,
b) at least one heat-activated expanding agent,
c) at least one heat-activated binder and
d) at least one adhesive by which the elastically compressible particles and the other constituents are joined to form the composite block.
The closure according to the invention is easy to make and may consist largely or entirely of recycled material. The closure according to the invention has excellent mechanical properties, particularly in regard to strength, abrasion resistance and elasticity. The closure according to the invention also has excellent fire-resistant properties. It may readily be formulated in such a way that it has a fire resistance of  greater than F90 according to DIN 4102. Its fire resistance is thus of the same order as that of concrete components which is particularly advantageous.
In the event of fire, the heat-activated expanding agent leads to an increase in volume and provides for particularly tight sealing of the opening. Also, additional voids are created which increase heat insulation. The at least one heat-activated binder becomes tacky under the effect of heat and ensures that the individual constituents of the composite block hold together and do not disintegrate into crumbs in the event of fire. In one advantageous embodiment, at least two heat-activated binders kicking in at different temperatures are provided. Suitable heat-activated binders are, in particular, organic thermoplastics which melt at low temperatures, inorganic hotmelt adhesives, such as borates, ammonium polyphosphate, which softens over a broad temperature range and at the same time has flame-retardant properties, and glass which develops its adhesive properties at relatively high temperatures. The glass is preferably present in fine-particle form, more particularly in the form of fibers, hollow microbeads or glass powder, in particular to avoid separation of the raw materials.
In one preferred embodiment, at least two expanding agents expanding at different temperatures are provided as expanding agents. This also enables the expansion properties to be controlled over a broad temperature range. Particularly suitable expanding agents are expanded graphite andxe2x80x94where expansion is also desirable at high temperaturesxe2x80x94unexpanded vermiculite and/or perlite.
To produce the composite block, the individual constituents may be premixed in fine-particle form and then mixed with the adhesive which is preferably sprayed onto the stirred mixture. The mixture wetted with the adhesive is then press-molded into a block, preferably under the effect of heat which may be uniformly introduced into the mixture, more particularly by a pulse of steam.
In one preferred embodiment of the invention, the at least one expanding agent and the at least one heat-activated binder are present in the form of granules containing both constituents. Highly uniform distribution of the constituents in the closure is obtained in this way, resulting in highly uniform mechanical and fire-retardant properties. Particularly suitable granules of this type are described as a swelling agent composition in DE 39 30 722 A1. Reference is expressly made here to the disclosure of that document. In general, the composite blocks are made up of 10 to 50% by weight and more particularly around 40% by weight of elastically compressible particles, 20 to 70% by weight and, more particularly, 40 to 60% by weight of the combination of heat-activated expanding agents and heat-activated binder and 0.5 to 20% by weight and more particularly around 10% by weight of adhesive. The combination of heat-activated expanding agent and heat-activated binder generally splits up into 40 to 80% by weight and more particularly 30 to 50% of expanding agent, more particularly expanding agent mixture, and 60 to 20% by weight and more particularly 70 to 50% by weight of binder, more particularly binder mixture.
In one preferred embodiment, the adhesive which holds the constituents of the composite block together is a diisocyanate, more particularly diphenyl methane diisocyanate, which is preferably set with water. The water of the steam pulse or the aqueous medium with which the adhesive is added may be used for setting. In another preferred embodiment of the invention, the adhesive which holds the constituents of the composite block together is a thermoplastic, more particularly a thermoplastic which can be applied in an aqueous medium, for example in the form of a dispersion. This thermoplastic may simultaneously act as the heat-activated binder. Examples of such thermoplastics are polyvinyl acetate/ethylene copolymers and polyvinyl acetate/ethylene/vinyl chloride terpolymers.
The closure according to the invention is preferably porous and, more particularly, has a rough surface. On the one hand, this makes it particularly compressible. On the other hand, the rough surface provides for effective adhesion in the openings to be closed.
Interestingly, it has been found that, despite its heterogeneous composition, the closure according to the invention has the properties of a homogeneous material. This is partly attributable to the fact that the particle sizes of its individual constituents, more particularly the elastically compressible particles, are different which provides for a uniform and dense packing. The elastically compressible particles may be substantially solid, such as pieces of rubber or pieces of cork. However, they are preferably porous. Thus, in one preferred embodiment, the composite block is a composite foam block while the elastically compressible particles are foam particles. Other suitable compressible particles are balls of fibers. Fibers and other compressible particles may also be present in combination with one another. In preferred embodiments, the elastically compressible particles have open pores, as is the case with fiber balls and open-cell foam particles. With open-pore particles such as these, relatively small constituents of the mixture can partly penetrate into the pores which further promotes homogeneity. The particle size of the individual constituents can vary within wide limits. In the case of the compressible particles, it is generally between 1 and 20 mm and more particularly between 1 and 5 mm. The other constituents may be present in the form of powders or particles with a particle size of 0.001 to 10 mm, preferably 0.1 to 5 mm and more preferably 0.3 to 5 mm.
As mentioned above, the closures according to the invention are preferably made from relatively large blocks. Sheets of suitable thickness can be cut from these blocks. This is easily done because the constituent material of the composite block is easy to cut, for example with knives, scissors or hot wires. The sheets can also be stamped out from the blocks. In this way, any size and shape of closure can be produced without having to keep a supply of special molds. The waste accumulating can readily be recycled by being used as elastically compressible particles in the production of new composite blocks. Sincexe2x80x94in that casexe2x80x94these particles already contain the heat-activated binders and expanding agents, their quantities can be reduced accordingly. It is also possible with advantage to prepare holes and openings for the passage of lines in the closures, for example by partial stamping.
Since the density of the starting materials is generally of the order of 1, the closures correspondingly contain 800 to 400 and, more particularly, 750 to 600 l gas/m3. The elasticity modulus of the closures is generally in the range from 1xc2x7103 to 1xc2x7105 N/m2, preferably in the range from 4 to 10xc2x7103 N/m2 and more preferably of the order of 7xc2x7103 N/m2. The closures advantageously have a compression hardness (at 40% compression) of 1xc2x7102 to 7xc2x7103 N/mm2, preferably 1.3 to 5xc2x7102 N/mm2 and more preferably of the order of 1.7xc2x7102 N/mm2. The Shore A hardness values of the closures is preferably in the range from 10 to 40, more preferably in the range from 12 to 20 and most preferably of the order of 15. These mechanical properties can be suitably varied by controlling the production conditions.
Other features and advantages of the invention will become apparent from the following description of Examples in conjunction with the subsidiary claims. In one embodiment of the invention, the individual features may be present either individually or in various combinations with one another.